What are you using for the reference when measuring the rail voltage?
Did you have your scope probe grounded to pin 3 when you checked the waveform?
Did you have your scope probe grounded to pin 3 when you checked the waveform?
The probe has been grounded to IC6 pin3 for all recent scope shots but the rail voltage was measured using a voltmeter grounded to input GND terminal.
With the scope grounded to the same point, check the signal on both sides of the resistor you pulled. Which side has the strange, distorted waveform you've been seeing?
There is no visible signal on either side of R151. The funny waveform is on both sides of R159 which sits between IC6 pin7 and ICU pin5. The amplitude is greater on the IC6 side but the waveform is identical. It is still there with R151 lifted and the ground jumper removed and the amplifier powers up and remains on but the output of ICU pin7 is still not clean. The ground jumper doesn't allow the amplifier to remain on.
I remeasured with the voltmeter and the rail voltage is ±67v. I may not have been applying the ground probe properly before...
I remeasured with the voltmeter and the rail voltage is ±67v. I may not have been applying the ground probe properly before...
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Do you still have the noise waveform on the speaker output?
If so, how do the waveforms on each side of R162 compare?
If so, how do the waveforms on each side of R162 compare?
R162 doesn't connect to pin 7 of IC6 according to the diagram.
Do you have a square wave on pin 7 of IC7?
Do you have a square wave on pin 7 of IC7?
R162 is not directly connected to IC6 pin7 but it is connected through R161 then R158 then IC6 pin7. I do not currently have a square wave on IC7 pin7, nor do I have a square wave on the inductor input either. The intermittent square wave is not showing up currently no matter how many times I cycle the amp or touch different places on the board.
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Do you have a 0.1uf cap that you can parallel across C134? If so, install it and repost the waveform on the IC side of R162.
Installed a .1uf capacitor across C134. I had removed the inductor so these readings were taken with the inductor out but the amp shuts down when the inductor is reinstalled. The high current draw seems to be greatly reduced since adding this capacitor, and it cleaned up the readings of IC7, but the amp won't stay on with the inductor reinstalled.
